In studies on chronic central nervous system diseases, markers for tumor involvement in the CNS of patients with Burkitt's lymphoma were described. Elevated antibodies to Epstein-Barr virus, myelin, basic protein and cerebroside were detected. Oligoclonal IgG was demonstrated and immune complexes were found in CSF of these patients. Immunoregulatory deficiencies were potentially described in homosexual males who heavily used amyl nitrite. In studies of patients with multiple sclerosis, immune complex levels were found to vary with disease exacerbation in MS patients but antibody levels to several viruses were shown to remain unchanged. In studies regarding JC virus pathogenesis, JC virus DNA was demonstrated in brain tumors and tumor cell lines from owl monkeys inoculated with JC virus. Cloned JCV DNA was transfected into oligodendroglial cells and infectious virus was recovered.